Abstract
Rapid and simple methods are required to detect viable pathogenic microbes in foods and drinks. In this study, fluorescent vital staining was used for the rapid enumeration of Escherichia coli O157 with physiologic activity in drinking water. FITC-labeled antibody (FA) was used for the specific detection of target microbes. 5-Cyano-2, 3-ditolyl tetrazolium chloride (CTC) was used to enumerate respiring bacteria. Natural mineral water was inoculated with E. coli O157:H7 cells, and analyzed by both fluorescent microscopy and flow cytometry following double staining with FA and CTC. Respiring E. coli O157:H7 cells inoculated into natural mineral water showed strong fluorescence of both FA (green) and CTC (red), thus they could be clearly and specifically distinguished from respiring indigenous bacteria or inactive cells in natural mineral water. A good correlation was achieved in flow cytometric analysis between the numbers of inoculated viable E. coli O157:H7 and those determined by flow cytometry. Respiring E. coli O157 cells in natural mineral water can be detected specifically by this method within a few hours. This double staining method with flow cytometry may be useful for microbial monitoring of drinking water.
